After marrying, she moved back to Bristol south to raise her son. She then studied for a social science degree at Bristol Polytechnic, where she gained a BA (Hons). Whilst working, she then continued her studies at the University of Bristol, conducting Ph.D research into women and housing.

She found fame in 1989 by asking Margaret Thatcher if the only hope for low-paid women was "to follow her example and find herself a wealthy husband". She was reading out a question on behalf of Ann Clwyd, at the time, who had "lost her voice".

At the time of her election, she was regarded as a hard left-winger and is still often referred to by the media as "Red Dawn", but became a New Labour loyalist and "absolutely loyal to New Labour",[5] leading Andrew Roth of The Guardian to say she has "changed from 'Red Dawn' to 'Rosy Pink'";[6] as part of this change, she has moved from support of CND, the rise of which originally encouraged her into politics, to voting for the renewal of Britain's Trident nuclear defence.[7] She also unsuccessfully lobbied the Soviet government of Mikhail Gorbachev to rehabilitate Leon Trotsky.[8]

As Paymaster General, Primarolo was responsible for the administration of the Tax Credits system, intended to provide working families with financial support. However, the administration of this system received significant criticism, including allegations that some families were left less well off as a result.[10] In 2003, a Treasury select committee member accused her of "losing control of [her] department"[11] after it became known that Inland Revenue buildings under Primarolo's purview had been sold to tax-haven companies.[11] This came shortly after she had "insisted ... the Child tax credit scheme was a 'success'", despite Inland Revenue staff walking out in protest against the pressure under which they were placed.[11][12] She was also responsible for introducing the controversial IR35 tax rules which were designed to tax "disguised employment" at a rate similar to employment. The measure was controversial as it was seen by some as unfair.[13][14] Primarolo was also the longest serving Paymaster General in the office's 200-year history.[15] Primarolo was named Chairman of the Code of Conduct Group upon its establishment by ECOFIN in March 1998.[16]

In 2005, PMTony Blair was forced to apologise after a report by the Parliamentary Ombudsman that Primarolo had failed to give Parliament accurate information. Primarolo admitted at the same time that she had been fully aware "about the extent of the problems".[17]

As Minister of State for Public Health she was responsible for health improvement and health protection issues including such areas as tobacco, obesity, drugs and sexual health, as well as international business, pharmacy and research and development.[18]

Primarolo's abilities as a minister have been questioned, with former Prime Minister Tony Blair revealing in his autobiography A Journey that he did not think she was "right for government" but had to give her a job because she was one of Gordon Brown's key allies;[20] and political commentator Danny Finkelstein arguing that she was "contender no. 1" for title of "Labour's worst Minister".[21]Jonathan Powell, Blair's Chief of Staff, is reported as saying "We fired Dawn Primarolo about ten times. And each time Gordon (Brown) insisted we put her back."[22]